I purchased the lens from Calumet, through Amazon. As soon as I took it out of the package, I put it on the 40D and made a few test shots in the studio. Like many, I used a print page shot at a 45 degree angle to the lens. At 5.6 there was nothing focused in the shot. Every part of the image was soft. I stepped the aperture down to f11 and f22 and used one speedotron strobe in a softbox to light the book page. Again, not a single focused point in the image. Even though I was already greatly disappointed and discouraged, I decided to do some outside shots with it to see how it performed. As you can see in the photo, there is not a sharply focused part of the image. I was using single point AF with it placed on the eyes. Aperture was f8, 1/125 at ISO 200. Fill flash was used as well. To add to that, the bokeh at any aperture was horrendous. At wide open, f2.8, the bokeh looked like broken glass or giant pixelation.
Luckily, Amazon accepted my return of the lens and I purchased the Canon L glass replacement. My honest opinion is that I would not suggest this lens to anyone. This had to be the most horrid piece of glass I have ever had on my camera. Many reviewers state that it has taken them several returns to Sigma to get one of these lenses that worked properly. As a professional photographer, I did not have the time to waste on returns and repair. If you are serious about shooting quality photos with a Canon product, then stick with Canon lenses.
